Interpretive Summary: This report describes the public health investigation of the largest documented outbreak of STEC O111 in a correctional facility. Although other enteric pathogen outbreaks have been reported in correctional facilities, most are attributed to foodborne and person-to-person transmission of bacterial and viral agents. Animal-to-human contact in a correctional facility dairy resulting in illness, or illness occurring as a result of inmate exposure to environmental contamination transferred from the dairy into the correctional facility has not been documented.

Technical Abstract:
In 2010, the Colorado Department of Public Health and Environment (CDPHE), the CDC National Institute for Occupational Safety and Health (NIOSH), and the High Plains Intermountain Center for Agricultural Health and Safety (HICAHS) partnered to investigate a Shiga toxin-producing Escherichia coli O111 (STEC O111) outbreak at a correctional facility (Facility A) in Colorado. Between April and July 2010, 10 inmates at Facility A received a diagnosis of laboratory-confirmed STEC O111. Pulsed-field gel electrophoresis (PFGE) testing found that the human STEC O111 isolates matched STEC O111 isolates from cattle at the onsite dairy. Findings suggested that inmates employed at the dairy could have been infected with STEC O111 or transported contaminated clothing or other items into the main correctional facility and kitchen, thereby exposing other inmates. This report describes the epidemiologic and occupational investigations which contribute to the understanding of STEC O111 and associated prevention and control measures appropriate for outbreaks in correctional facility settings.